"Reading the results dispassionately, young people today not what they used to be. Some well chosen words, a little bit gruff, she rolls her eyes, she's had enough."

Now Sir Alan Sugar's sidekick Margaret Mountford really has had enough after it was revealed on the eve of last night's Apprentice finale that she was quitting the show to concentrate on her PhD in papyrology. How very Margaret.

Mountford, a former solicitor who became a non-executive director of Sugar's Amstrad 10 years ago, emerged as the real star of the show over the course of five series of The Apprentice. Who can possibly replace her, and will Nick Hewer be half the man he was without his fellow sidekick?

"Nobody does withering like Margaret," said Adrian Chiles. And he's not kidding, with this fabulous put-down of Michael Sophocles in series four after he struggled with the concept of kosher. "It defies belief," said Hewer. "He did classics at Edinburgh, how could he make such a mess of it?"

Cue Margaret: "I think Edinburgh isn't what it used to be."

But then Mountford thought Sophocles was a waste of space. His over-enthusiastic boardroom celebrations earlier in the 2008 series probably didn't help. Sugar just looked dumbfounded. Mountford was downright appalled.

Mountford, a mistress of understatement, says what everyone else is thinking – without quite saying it – in discussion with Simon Ambrose, the eventual winner of series three, over his plans for a new building next to the River Thames. "I'm glad it's not going out before the watershed."

And here she is with series four finalist Alex Wotherspoon, with my particular favourite Mountism, if you will. "Alex, you stepped so far back from it you were practically out of the room." Keep watching for Margaret and the comedy bum shot. I must have missed that one.

Mountford's quickfire wit put Chiles in his place on BBC2's The Apprentice: You're Fired, when Chiles suggests she should stand for high office. She looks appalled. "Higher than The Apprentice?"

And she even had Sugar lost for words when she compared one of this year's contestants, Lorraine Tighe, to the Cassandra legend whose prophetic insights, it says here, were ignored until after they had come to pass. "Do you know who she is?" asked Mountford. Nobody moved, and even Sugar shifted a little nervously in his chair.

Farewell, then, Margaret Mountford, and good luck with the PhD. TV executives are, as we speak, scrambling to commission a new primetime documentary: Margaret Mountford: Papyrology and Me.

In the meantime, console yourself with this tribute from Joe Cornish, of Adam & Joe fame, composed for his BBC 6Music radio show.

All together now: "A handsome woman with so much dignity, Margaret Mountford your hair is like a cloud. Your lips so red and your eyes strong and proud..."